1. Field of the Invention
The present invention relates to a device for enabling so-called bracketing exposure operation, in which exposure operation is conducted with a predetermined exposure value and at least another exposure value determined by slightly varying said predetermined exposure value, thereby photographing an object with slightly varied exposure values respectively on different film frames.
2. Related Background Art
Bracketing exposure device is already disclosed for example in the U.S. Pat. Nos. 3,762,285 and 4,734,727, and camera systems with such exposure function are already available commercially.
In such known bracketing exposure operation, there are designated a start exposure value for the first exposure, the amount of shift in exposure value between frames and the number of frames to be photographed, prior to an exposure starting operation, whereby exposure are made on the film frames of the designated number, starting from a first exposure with the designated start exposure value, with stepwise shifted exposure values toward the overexposure side. However, the controllable range of exposure value, namely diaphragm aperture and shutter speed, is limited in the camera. In the commercially available camera systems, therefore, the number of exposure frames and the amount of shift in exposure value between the frames in the bracketing exposure mode are limited within a certain finite range, so that the exposure value in each frame in the bracketing exposure operation does not exceed the upper or lower limit of the exposure value set in the camera, as long as the designation is made within said range. More specifically, the maximum limit of the range of each designated value is so defined that the exposure values in the bracketing exposure operation does not exceed the upper limit of the exposure value determined in the camera in any combination of the start exposure value, number of frames and shift of exposure value between frames.
However, in such limitation of ranges, even when the number of frames to be photographed is selected at the minimum value, the amount of shift in exposure value between the frames is limited by the same condition as when the number of frames is selected at the maximum value. Consequently, the shift in exposure value becomes limited though there is still an enough margin to the upper limit of the exposure value defined in the camera.